1. Technical Field
The present invention relates to methods and instruments used in minimally invasive surgical procedures. In particular, the present invention relates to an instrument port including a flushing system to prevent the introduction of emboli into a surgical site.
2. Description of the Related Art
It is generally accepted that minimally invasive cardiac procedures are more desirable than open heart procedures. Open heart surgery generally requires sawing open the patient's sternum to gain access to the heart. During this surgery, the heart is stopped while catheters and other instruments are inserted into the veins and arteries of the heart. Open heart surgery causes trauma to the patient's chest. In contradistinction, minimally invasive procedures do not require direct access to the heart and almost always provide the patient with shorter recovery times and substantially less pain.
There are three different types of minimally invasive cardiac procedures: Minimally Invasive Direct Coronary Bypass (MIDCAB), Off-Pump Coronary Artery Bypass (OPCAB), and Robotic Assisted Coronary Artery Bypass (RACAB). The MIDCAB procedure is used to remove blockages from the front of the heart and does not require splitting the sternum. A small incision is made in the chest, the muscles are moved, and a small piece of the costal cartilage is removed to gain access to the heart. A heart-lung machine is also commonly used during this procedure. The OPCAB procedure is generally the same as the MIDCAB; however, a heart-lung machine is not used. In both of these procedures, a device can be used to restrict movement of the heart so that it can still beat during the operation. RACAB also does not require the sternum to be cut, and the patient is operated on by robots that are controlled by surgeons. Each of these procedures results in a lower risk to the patient of stroke, lung or kidney problems, and lack of mental clarity, as well as a faster recovery time and lower hospital costs.
Endoscopic surgery can be utilized with each of the above procedures, especially with RACAB. An endoscope is a tubular optical system for viewing the interior of an organ or body cavity. By making a small incision, a hollow tube, or port, can be inserted into the patient to a site of surgery or tissue area, and an endoscope can be inserted into that port for observation and monitoring during surgery. Various other incisions and ports can be created for the insertion of various instruments such as instruments for manipulation, grasping, cutting, and coagulation for use during surgery.
While some open surgical procedures have been adapted to endoscopic techniques, there are limitations, particularly with more complex procedures. Fundamental problems relate to the access ports used for inserting the various manipulative instruments. While limiting incisional trauma, the small diameter of these ports limits the size and design of the inserted instruments. To achieve similar function as in open surgery, equipment becomes complex and therefore more expensive. There is also added risk with each inserted port because each port requires puncturing the body wall, risking injury to contained viscera with each puncture.
Equally important has been the impact on the surgeon's ability to manipulate tissue. While the visual field may have been improved, tactile sensation, depth perception, and proprioceptive awareness of tissues have been markedly reduced by instruments that insulate the surgeon from the operative field. Furthermore, the limited access enabled by each port dictates that multiple ports be used. As procedural complexity increases, the surgeon must adapt to a continuously changing and less predictable environment. Further, as the number of ports increases, the risk and incidence of complications increases. The requirement for highly skilled and coordinated surgical teams also increases. This has resulted in long learning curves and has limited wide application of these procedures for complex cases.
A trocar is commonly used to puncture the body wall to aid in the introduction of ports that allow for the insertion of endoscopes and instruments into the body cavity. The trocar has a sharp end designed to pierce the skin as the surgeon presses it down. It may also pierce the underlying viscera unless great care is taken, particularly in view of the flexibility of the body wall. The trocar includes a cannula or tube used for drainage or for the insertion of an instrument into the body cavity. Since it is desirable to minimize the patient's wounds, there is an effort made to minimize the size of an incision associated with trocar use. As a result, the size of the cannula used in the trocar-created incision is generally small. It therefore can only be used to pass relatively small instruments into the body cavity. Moreover, the narrow cannula severely restricts maneuverability of the device contained therein. Therefore, though trocars offer the advantage of wound minimization, they are of some danger to the viscera, they are of restricted dimensions for allowing the passage of instruments of interest therethrough, and they permit limited tactile manipulation.
HeartPort, Inc. created an integrated system of cannulae and catheters to reach the patient's heart. The system enabled the manipulation of instruments through small ports between the ribs. However, there were several problems with their system. First, the patient still had to undergo cardiopulmonary bypass (CPB) in order to have the minimally invasive cardiac procedure performed. More importantly, however, was that air introduced by instruments into the arrested heart had to be removed prior to restarting the heart. If this air was not removed, the patient could suffer serious medical complications such as a stroke. The HeartPort, Inc. system had no way of removing/degassing air from inserted instruments or from pockets formed in the arrested heart.
Research recently showed that it is possible to perform minimally invasive cardiac procedures on beating hearts (Suematsu, et al., “Three-dimensional echocardiography-guided atrial septectomy: An experimental study,” Journal of Thoracic and Cardiovascular Surgery (2004) 128: 53-59). In order to make such a surgery feasible, a device is needed that prevents air from entering the chambers of the heart, as these emboli could cause a stroke in a patient.
U.S. patent application Ser. No. 10/580,144 to Cannon and del Nido discloses a trocar including an insertion end having a fluid and air-tight chamber. The chamber is made fluid and air-tight via a sealing device. The trocar also includes an agitator to move air or foreign objects from the insertion end to an opposite end so as to keep the air or foreign objects away from the body into which the trocar is inserted. Two lumens are located within the trocar: an instrument lumen and a downflow lumen. An inlet port allows for the flow of inert fluid through the downflow lumen and out through an outlet port proximate to the instrument lumen to force out any air bubbles in the trocar away from the insertion end.
There is therefore a need for a method for introducing surgical tools and/or imaging equipment into the chambers of a still-beating or arrested heart. There is a further need to eliminate the introduction of air into the chambers of the heart during the course of the surgery. There is also a need to limit the amount of blood lost from the heart chamber into the chest cavity of the patient, as well as limit blood flow into the instrument through a trocar while in the operating room. There is further a need to make the instrument port compatible with current imaging techniques, such as 3-D ultrasonic imaging, to allow the instrument port to be easily visualized during minimally invasive procedures.